1. Field of the Invention
The invention relates to accumulator-type (common rail type) fuel injection apparatuses, and internal combustion engines provided with those accumulator-type fuel injection apparatuses, that are furnished with an accumulator piping (so-called “common rail”) that is adopted for the fuel supply system of internal combustion engines (such as diesel engines). In particular, the invention relates to measures for allowing the idling revolution to be set low while suppressing vibration of the internal combustion engine, and measures for making it possible to adjust the common rail internal pressure with high precision.
2. Description of the Related Art
In the past, accumulator-type fuel injection apparatuses, which have superior controllability compared to mechanical fuel injection pump-nozzle type apparatuses, have been proposed as the fuel supply system in multi-cylinder diesel engines, etc. (for example, see Patent Documents 1 and 2 listed below).
Such fuel injection apparatuses hold, in a common rail, fuel that has been pressurized to a predetermined pressure by a high-pressure pump, and this fuel that is held in the common rail is injected into the combustion chamber from a predetermined injector in accordance with a fuel ejection timing. A controller performs calculations to control the fuel pressure within the common rail (hereinafter, called the common rail internal pressure) and the injectors so that fuel is injected under the most suitable injection conditions for the operating state of the engine.
Thus, in accumulator-type fuel injection apparatuses it is possible to control not only the fuel injection amount and the injection timing, but also the fuel injection pressure, which is determined by the common rail internal pressure, according to the operating state of the engine, and thus they have gained attention as injection apparatuses with excellent controllability. In particular, such accumulator-type fuel injection apparatuses have favorable pressure increase properties in the low revolution region of the engine, and thus high-pressure fuel injection is possible from the low revolution region and it is possible to perform the idling operation at low revolutions, which was unachievable with conventional mechanical-type fuel injection apparatuses. Specifically, in conventional mechanical-type fuel injection apparatuses it was only possible to achieve low revolutions of about 500 rpm, but with accumulator-type fuel injection apparatuses it is possible to achieve idling operation at about 250 rpm. Because idling operation can be performed at low revolutions, it is possible to achieve a reduction in noise and conserve fuel use during idling operation.
Fuel pumps that are provided with a plurality of pressurized fuel supply systems, such as that disclosed in the following Patent Document 3, are known as an example of the high-pressure pump that is used in this type of accumulator-type fuel injection apparatus    Patent Document 1: JP 2000-18052 A    Patent Document 2: JP 2003-328830 A    Patent Document 3: JP 2004-84538 A